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Quick answer from a licensed plumber: A toilet flange that sits below the finished floor is the most common cause of a toilet that leaks at the base, rocks, or smells — and stacking wax rings is not the fix. Oatey, who make the flanges, put the target plainly: “The flange should sit on top of or even with the finished floor.” If yours is lower than that, raise it with a flange spacer or extension kit. If it is only level with the floor, a jumbo wax ring is a legitimate answer.
At a Glance
| Flange position | What to do |
|---|---|
| On top of the finished floor | Correct — standard wax ring |
| Even with the finished floor | Acceptable — jumbo/extra-thick ring |
| Below the finished floor | Raise it — spacer or extension kit |
| Broken or corroded ears | Repair ring, or replace the flange |
| Any depth — two wax rings stacked | ⛔ Don’t. This is the failure, not the fix. |
Why this happens — almost always new flooring
The flange was set correctly when the house was built. Then someone laid tile, or LVP, or a second layer of underlayment over the original floor, and did not touch the flange. The floor came up half an inch; the flange stayed where it was. Now it is buried.
This is why the problem shows up as “the toilet was fine until we redid the bathroom.” The toilet did not change. The floor did.
The other route to the same place is a corroded cast iron or steel flange in an older house, where the ring has rusted down and the bolt ears have broken off. Same symptom, different repair.
What actually goes wrong when the flange is too low
The wax ring is a compression seal. It is designed to squash a specific amount between the toilet horn and the flange. Set the flange too deep and the toilet never reaches proper compression — Oatey’s guidance on a low flange is blunt about the consequence: “The wax ring may not seal properly.”
What you get from that, in the order people usually notice it:
- A smell that comes and goes. Sewer gas escaping past an incomplete seal. People chase this for months and blame the trap.
- A rocking toilet. The china is resting on the wax instead of on the floor.
- Water at the base after a flush — often only a few drops, often only sometimes, which is exactly why it goes unnoticed until the subfloor is soft. See a toilet leaking at the base for the full symptom list.
The slow version of this is the expensive one. A seal that weeps a little with every flush rots the subfloor from above, and by the time the floor feels spongy you are replacing plywood and possibly joist tops, not a $4 wax ring.
⛔ The mistake: stacking two wax rings
This is the single most common wrong answer to a low flange, and it is worth being direct about.
Two stacked rings do not compress as one. The upper ring squashes, the lower one shifts, and the joint ends up with a wandering, unsupported seal that is thicker but not tighter. It also raises the toilet enough that it rocks — and a rocking toilet destroys whatever seal it did have, because the wax gets worked back and forth every time somebody sits down.
It sometimes holds for a year. That is the trap: it works just long enough that people believe it is a real repair, and it fails somewhere hidden.
Use one ring, and change the flange height instead.
The right fixes, in order
1. Flange is level with the floor → jumbo wax ring
This is a legitimate, code-neutral answer. Oatey state it directly: “if the flange is even with the finished floor, you can use a jumbo or MaxWax® ring to achieve a secure, watertight seal.” One thicker ring — not two standard ones. This is the cheapest correct fix and it covers a lot of real bathrooms. See the best toilet wax rings, including the repositionable rubber seals that tolerate an imperfect flange better than wax does.
2. Flange is below the floor → spacer or extension kit
This is the actual repair for a buried flange. Oatey’s guidance: “If the flange sits too low, use a flange spacer or extension kit such as the Oatey® Set-Rite® Toilet Flange Spacer System to raise it to the correct height.”
These kits stack rigid spacer rings to make up the height, sealed between layers, and bolt through to the subfloor. Measure the gap from the top of the flange to the finished floor first and buy for that dimension — this is a measure-once job, and guessing means a second trip.
3. Bolt ears broken or flange corroded → repair ring
A repair ring (sometimes called a half-moon or flange repair plate) is a metal ring that goes over the damaged flange and gives you fresh bolt slots. It fixes broken ears; it does not fix height. If the flange is both broken and buried, you need the repair ring and the height corrected.
4. Everything is wrong → replace the flange
The real repair, and the only one that is unambiguously right. It means cutting the old flange off the pipe and fitting a new one at the correct height. On PVC that is straightforward; on cast iron it is a bigger job and a reasonable place to call somebody. Our walkthrough of replacing a toilet covers the reset either way.
Fasten it to the subfloor, not the finish floor
Whatever you do about height, the flange has to be anchored properly or the whole repair moves. Oatey’s guidance is to “always use rust-proof screws to anchor the flange to the subfloor,” and to match the hardware to what you are anchoring into — “Concrete: Use concrete anchors. Wood: Use wood screws.”
Screwing a flange into a half-inch of tile or vinyl alone gives you a flange that lifts under load. The screws need to reach structure.
Before you put the toilet back
- Dry-fit it. Set the toilet with no wax and check that it sits flat on the floor and does not rock. Fix the rock now, not after the wax is committed.
- Shim if needed, then trim the shims. A toilet that rocks will break its seal no matter how good the flange height is.
- Set it once. Lower it straight down and do not twist it into place — twisting smears the wax and opens a leak path.
- Do not overtighten the closet bolts. Snug, alternating side to side. China cracks and the crack is often invisible until it leaks.
Fresh wax every time the toilet comes up, without exception. A used ring will not re-compress. Full detail in how to replace a toilet wax ring.
The part that fixes it
Heads up: the product links below are Amazon affiliate links — you pay no more, and as an Amazon Associate we earn from qualifying purchases.
- Fluidmaster 7513 extra-thick wax ring with flange — the standard fix when the flange sits a little below the finished floor.
Wax vs wax-free, and when each wins: our wax ring guide.
Often the better answer for a low flange: a wax-free seal tolerates the gap and can be reset if the bowl shifts, where stacked wax rings squash and leak. Fluidmaster 7530P8 wax-free seal.
FAQ
How high should a toilet flange be?
Oatey state that “the flange should sit on top of or even with the finished floor.” On top is ideal; even with the floor is workable using a thicker wax ring. Below the finished floor is the condition that causes leaks and needs correcting with a spacer or extension kit.
Can I use two wax rings if my flange is too low?
No. Stacked rings do not compress as a single seal — the top one squashes, the bottom one shifts, and the toilet often ends up rocking, which works the wax loose. It can hold for a while, which is exactly what makes it dangerous. Use one jumbo ring if the flange is level with the floor, or raise the flange properly if it is below.
What do I use if the flange is below the finished floor?
A flange spacer or extension kit. Oatey’s guidance is to “use a flange spacer or extension kit such as the Oatey® Set-Rite® Toilet Flange Spacer System to raise it to the correct height.” Measure the gap from the top of the flange to the finished floor before buying so you get the right stack height.
Why does my toilet rock even after a new wax ring?
Usually because the flange height is wrong, so the toilet is resting on wax instead of on the floor — or because the floor is uneven. Dry-fit the toilet with no wax to find out which. If it rocks dry, shim and trim it; if it only rocks with wax under it, the flange is too high or you have stacked rings.
Does a flange repair ring fix a low flange?
No. A repair ring restores broken bolt ears on a damaged flange; it does not raise the flange to the correct height. If the flange is both broken and too low, you need the repair ring plus a spacer — or a full flange replacement.
Sources
- Oatey — Five Best Practices When Installing a Toilet Flange: “The flange should sit on top of or even with the finished floor.” · “if the flange is even with the finished floor, you can use a jumbo or MaxWax® ring to achieve a secure, watertight seal.” · “The wax ring may not seal properly.” · “If the flange sits too low, use a flange spacer or extension kit such as the Oatey® Set-Rite® Toilet Flange Spacer System to raise it to the correct height.” · “Always use rust-proof screws to anchor the flange to the subfloor.” · “Concrete: Use concrete anchors. Wood: Use wood screws.”
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